Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $201.26   12.699%   $226.818   $226.82   $226.80   $226.80  
  Purchase #2 $120.42   4.667%   $126.04   $126.04   $126.05   $126.00  
  Purchase #3 $235.31   11.209%   $261.6859   $261.69   $261.70   $261.70  
  Purchase #4 $63.25   6.152%   $67.1411   $67.14   $67.15   $67.10  
  Purchase #5 $155.99   9.225%   $170.3801   $170.38   $170.40   $170.40  
  Purchase #6 $121.50   3.541%   $125.8023   $125.80   $125.80   $125.80  
  Purchase #7 $220.39   4.562%   $230.4442   $230.44   $230.45   $230.40  
  7 purchase totals = $1,118.12       $1,208.3116   $1,208.31   $1,208.35   $1,208.20